Understanding Which Biomechanical and Neuromuscular Variables Are Important in Improving Discus, Shot Put and Hammer Throwing Performance
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Athletics has been a prominent feature in the Olympic programme for decades, within which rotational throwing events, discus, shot put, and hammer, comprise three of the four throwing events. Given the competitive nature of throwing, coaches and athletes are constantly seeking methods to enhance performance. In general, coaches and athletes look to improve either biomechanical (throwing technique) or neuromuscular (e.g. strength and power) abilities in an effort to improve performance. In isolation, both biomechanical and neuromuscular variables have been related to performance enhancement. However, conjecture exists as to the causal effect adapting neuromuscular variables has on enhancing performance, and changes in biomechanical variables over longitudinal periods have not been reported. Thus, the overall purpose of this Thesis was to understand which biomechanical and neuromuscular variables are important to improving discus, shot put and hammer throwing performance. While trying to address the current gaps in the literature with scientific rigour, this Thesis was designed in an applied manner as to be embedded within, and directly influence, coaching and resistance training practises. A paucity of resistance training literature to enhance rotational throwing performance was identified; as such, a conceptual model of resistance training to enhance neuromuscular drivers of throwing biomechanics was developed. It was found that biomechanical phenomena are underpinned by multiple neuromuscular factors. Therefore, a comprehensive assessment battery was needed to determine the neuromuscular variables associated with throwing performance, specifically, the appropriate sections of the force – time and force – velocity curves. Furthermore, metrics associated with muscular and tendinous qualities would provide additional adaptive information. It remains difficult to assess tendinous stiffness of upper and lower body tissues, and rotational ability in an applied setting. Thus, three assessment protocols were assessed: two were adapted from the literature and one was a novel protocol specific to shot put. The first assessment of musculoarticular stiffness derived from the perturbation method demonstrated poor test – retest reliability. More specifically, it was found that bench press and bench pull musculoarticular stiffness was unreliable [change in mean: -35.1 to 15.8%; coefficient of variation (CV): 7.1 to 111%; intra-class correlation (ICC): -0.58 to 0.89] and squat musculoarticular stiffness was not quantifiable in a group (n = 8) of experienced power trained athletes. The second and third assessments, seated cable rotation and cable put, were found to be reliable between days in a group (n = 9) of resistance trained men. Reliability was observed in the kinematic variables (cable put: ICC = 0.92 to 0.99, CV = 3.1 to 8.6%; cable seated rotation: ICC = 0.76 to 0.99, CV = -1.7 to 16.1%), but not the kinetic variables. Establishing the relationship between biomechanical and neuromuscular variables relies on reliable neuromuscular data being correlated to reliable biomechanical data. More specifically, the role of pulling musculature in throwing is not well understood. Thus, to understand the role of pulling type movements and throwing performance, kinematic measures from a throwing movement need to be reliable prior to performing correlations between such throwing kinematic measures and neuromuscular measures. Therefore, two investigations were performed: 1) the reliability of kinematics from a seated shot put, and 2), the relationship between seated shot put kinematics and bench throw and bench pull kinematics in a group of resistance trained athletes (n = 9). Firstly, seated medicine ball kinematics derived from manual digitisation were found to be reliable (CV = 2.75 to 8.38%, ICC = 0.82 to 0.95) between days. Furthermore, such kinematics were highly repeatable between digitisation occasions (CV = 0.12 to 4.98%, ICC = 0.92 to 1.00) and no difference in kinematics were observed when the number of digitised views was reduced from three to two. Secondly, bench pull bar velocity was highly related to seated shot put peak velocity, as was bench press (r = 0.71 to 0.89, p < 0.05). However, light load bench pull was highly related to seated shot put acceleration variables (r = 0.67 to 0.83, p < 0.05), whereas bench press was not. The differing association suggests that pressing and pulling musculature play different roles in putting ability and that both should be included in a comprehensive test battery of shot putters’ neuromuscular qualities. The last four investigations quantified changes in competition performance, throwing biomechanical variables, and neuromuscular variables over a longitudinal period in four throwers (shot put: n = 1 female, discus; n = 1 male; hammer throw; n = 2, 1 female 1 male) ranging in ability from sub elite to elite. All athletes were highly trained and were competitive athletes ranked in the top three in each discipline based on national rankings. Throwing biomechanics were assessed using video digitisation (hammer throw) or infra-red marker tracking and automated modelling (shot put and discus). The tracked neuromuscular variables remained constant between participants and included force-velocity profiling [countermovement jump, bench throw, bench pull, and cable rotation (hammer throw and discus) or cable put (shot put)], vertical jump, and inertial load ergometer testing. Over the tracking period, fluctuations in both biomechanical and neuromuscular variables were observed and the association between performance change and change in biomechanical or neuromuscular variables was specific to the athlete. For both the discus and shot put investigations, no biomechanical or neuromuscular variables changed concurrently with the criterion performance variable (release velocity); however, the female hammer thrower’s release velocity tended to change with change in velocity through the preceding turns, but not with any singular neuromuscular variable. Furthermore, many force velocity measures declined while release velocity increased. In contrast, the male hammer thrower showed a strong association between release velocity and changes in late eccentric squat ability, but not with changes in any biomechanical variables. It was proposed that the predictive ability of neuromuscular and biomechanical measures is athlete specific and should be treated as such. In summary, this Thesis identified that biomechanical and neuromuscular variables in isolation are not predictive of performance. However, all variables – both biomechanical and neuromuscular – should be enhanced, with much more research needed to determine whether predicting performance change from biomechanical and neuromuscular variables is viable in and valid for rotational throwing athletes.